Make errors configurable

synapse/api/errors.py

@@ -332,11 +332,14 @@ def __init__(
         self.previous_errcode = previous_errcode
         super().__init__(code, msg, errcode, additional_fields)
 
-    def error_dict(self) -> "JsonDict":
+    def error_dict(self, allow_unstable_fields: bool = False) -> "JsonDict":
+        fields = {}
+        if allow_unstable_fields:
+            fields["org.matrix.msc3848.unstable.errcode"] = self.errcode
         return cs_error(
             self.msg,
             self.previous_errcode,
-            **{"org.matrix.msc3848.unstable.errcode": self.errcode},
+            **fields,
             **self._additional_fields,
         )
 

synapse/config/experimental.py

@@ -90,3 +90,6 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
 
         # MSC3827: Filtering of /publicRooms by room type
         self.msc3827_enabled: bool = experimental.get("msc3827_enabled", False)
+
+        # MSC3848: Introduce errcodes for specific event sending failures
+        self.msc3848_enabled: bool = experimental.get("msc3848_enabled", False)

synapse/federation/federation_server.py

@@ -42,6 +42,7 @@
     IncompatibleRoomVersionError,
     NotFoundError,
     SynapseError,
+    UnstableSpecAuthError,
     UnsupportedRoomVersionError,
 )
 from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion
@@ -468,7 +469,12 @@ async def process_pdus_for_room(room_id: str) -> None:
                     )
                     for pdu in pdus_by_room[room_id]:
                         event_id = pdu.event_id
-                        pdu_results[event_id] = e.error_dict()
+                        if isinstance(e, UnstableSpecAuthError):
+                            pdu_results[event_id] = e.error_dict(
+                                self.hs.config.experimental.msc3848_enabled
+                            )
+                        else:
+                            pdu_results[event_id] = e.error_dict()
                     return
 
                 for pdu in pdus_by_room[room_id]:

synapse/handlers/auth.py

@@ -50,6 +50,7 @@
     LoginError,
     StoreError,
     SynapseError,
+    UnstableSpecAuthError,
     UserDeactivatedError,
 )
 from synapse.api.ratelimiting import Ratelimiter
@@ -562,6 +563,8 @@ async def check_ui_auth(
                     await self.store.mark_ui_auth_stage_complete(
                         session.session_id, login_type, result
                     )
+            except UnstableSpecAuthError as e:
+                errordict = e.error_dict(self.hs.config.experimental.msc3848_enabled)
             except LoginError as e:
                 # this step failed. Merge the error dict into the response
                 # so that the client can have another go.

synapse/http/server.py

@@ -57,6 +57,7 @@
     RedirectException,
     SynapseError,
     UnrecognizedRequestError,
+    UnstableSpecAuthError,
 )
 from synapse.http.site import SynapseRequest
 from synapse.logging.context import defer_to_thread, preserve_fn, run_in_background
@@ -155,14 +156,20 @@ def is_method_cancellable(method: Callable[..., Any]) -> bool:
     return getattr(method, "cancellable", False)
 
 
-def return_json_error(f: failure.Failure, request: SynapseRequest) -> None:
+def return_json_error(
+    f: failure.Failure, request: SynapseRequest, allow_unstable_fields=False
+) -> None:
     """Sends a JSON error response to clients."""
 
     if f.check(SynapseError):
         # mypy doesn't understand that f.check asserts the type.
         exc: SynapseError = f.value  # type: ignore
         error_code = exc.code
-        error_dict = exc.error_dict()
+        if f.check(UnstableSpecAuthError):
+            unstable_exc: UnstableSpecAuthError = f.value  # type: ignore
+            error_dict = unstable_exc.error_dict(allow_unstable_fields)
+        else:
+            error_dict = exc.error_dict()
 
         logger.info("%s SynapseError: %s - %s", request, error_code, exc.msg)
     elif f.check(CancelledError):
@@ -575,6 +582,14 @@ async def _async_render(self, request: SynapseRequest) -> Tuple[int, Any]:
 
         return callback_return
 
+    def _send_error_response(
+        self,
+        f: failure.Failure,
+        request: SynapseRequest,
+    ) -> None:
+        """Implements _AsyncResource._send_error_response"""
+        return_json_error(f, request, self.hs.config.experimental.msc3848_enabled)
+
 
 class DirectServeHtmlResource(_AsyncResource):
     """A resource that will call `self._async_on_<METHOD>` on new requests,